Answer:
The correct answer is inner transition metals.
Step-by-step explanation:
The elements of block f are often referred to collectively as inner transition metals and comprise lanthanides (or lanthanoids) and actinides (or actinoids). They constitute periods 6 and 7 of the periodic table of the elements respectively. They are characterized by having ionic radii and chemical behaviors, very similar to each other.
Lanthanides have the orbital 4f partially or completely full. They are known as rare earths as they are in the form of oxides and are present in nature, except for theium (Pm).
Actinides have the orbital 5f partially or completely full.